Patent GB-1458659-A (GB)
Title: Systems for automatically controlling vehicles
IPC: G07C5/08
Filed: 1972-09-08
Abstract: 1458659 Automatic control of speed HAWKER SIDDELEY DYNAMICS Ltd 28 Nov 1973 [8 Sept 1972] 10697/72 Headings G3N and G3R [Also in Division B7] In a control system for vehicles travelling on track 11 which is divided into blocks 12 and is equipped with passive track markers 15 e.g. permanent magnets, equispaced along the track which are detected on a vehicle to determine its speed, each vehicle in a block receives from a block transmitter 13 data representing the maximum allowable speed in the block and a distance aspect in terms of the number of track markers 15 to the next vehicle ahead which is representative of the maximum safe speed for the vehicle and the vehicle includes circuitry for selecting as required speed the lower of these two maximum speeds and for controlling its drive to bring the actual speed into agreement therewith. Each block has a block controller 16 including a vehicle presence detector 15 which co-operates with trackside coil 14 to detect a vehicle in a block and send this information via lines 17 to the next preceding nine block controllers and an aspect generator 19 which is coupled to the next succeeding nine block controllers to determine the position of the next ahead vehicle and provide this information in terms of marker numbers to the block transmitter 13. The correct and proper sequence of signals from the succeeding block controllers is checked by sequence checker 24. The block transmitter is also fed with the maximum block speed from generator 20 which can be altered by commands along a data highway from a central control. Active track markers can also be provided along the track and can be of two types - a first comprising an electro magnet which can be switched on thus providing an extra count to the vehicle which reacts by slowing down to compensate the apparent increase of speed and a second comprising an electromagnet adjacent one of the permanent magnets which when on cancels its effect thereby reducing the count to the vehicle which reacts by increasing its speed to offset the apparent reduction. The active markers are used to assist in respacing the vehicles along the track. The vehicle presence detector in each block is also connected to a central control via the data highway whereby the presence of a dummy vehicle in a block can be signalled so that vehicles approaching the block slow down and then come to a halt as if a real vehicle were present and stationary in the block. This system is used to bring vehicles to a halt at stations, by inserting a dummy in the next block in advance, this being removed when the vehicle is free to leave the station and is also used to control vehicles at track converging or diverging points. The distance aspect signal and the maximum speed signal are picked up on the vehicle by receiver 30 and the distance signal in terms of the number of track markers is fed to a reversible counter 32. The vehicle also carries a vehicle trajectory programmer 33 which supplies two outputs one on lead 34 representing a voltage analogue of the required speed and one on lead 35 representing the required speed in terms of pulses at a rate equal to the rate the vehicle must pass the track markers. This latter signal is fed back on line 36 to count down the number in counter 32 which however is repeatedly overwritten by the input from the data receiver. The output from the counter is applied via a digital-analogue converter 37 to a comparator 46 where the analogue distance voltage which is indicative of the maximum safe speed for the vehicle is compared with the required speed VD' from the programmer translated in unit 29 to a distance clear to run signal fVD'. In addition the maximum speed signal from the receiver after conversion in unit 39 to an analogue signal is compared in comparator 41 with the required speed signal VD'. The comparator outputs control via AND and OR gates 44, 45 a pair of switches connected in a +ve supply +VLIM and a -ve supply -VLIM to the input of an integrator 40 which supplies the required value of speed VD'. This analogue value is converted in pulse generator 49 to a marker rate demand and applied to the up input of a reversible counter 50 which has a down input supplied by track marker detector 52. The output error is converted to an analogue value and after scaling in unit 54 is applied to one input of an error summing circuit 55. The pulses from the marker detector are fed to a frequency to analogue converter 56 to provide an actual speed voltage which is fed via a low pass filter to comparator 58 where it is compared with the required speed value VD'. The comparator output is fed to a second input to the summing circuit 55. An output from tachogenerator 60 is supplied as a rate feedback voltage via a compensation circuit and high pass filter to a third input of the summing circuit to compensate for rapid speed fluctuations. The output of the summing circuit controls drive motor 67.